This application claims the benefit of PCT Serial No. PCT/GB99/02481, filed Jul. 29, 1999 and published in the English language.
The present invention relates to a double seal of unitary construction for hermetically sealing two substantially coplanar mating surfaces.
The shipment and storage of toxic, radioactive or otherwise hazardous material demands the use of containers which can be reliably sealed and tested for leak tightness. A sealing arrangement is described in GB 2175885 using two laterally spaced sealing members which together with the opposing surfaces of a container body and lid define an endless passage. By introduction of a pressurised gas, the endless passage can be used to verify the integrity of the sealing arrangement. The present invention aims to provide a seal suitable for use between a large steel box and a steel lid for transporting intermediate and low level nuclear waste.
The invention provides a double ring seal of unitary construction made from a resilient deformable material, comprising two coplanar sealing rings for use in sealing between two substantially planar surfaces, and means interconnecting the rings, whereby the rings form between them an interspace volume when the seal is in use. The interconnecting means may comprise a web dividing the interspace volume into upper and lower parts, said web having at least one aperture providing communication between said parts. The interspace allows the integrity of the seal to be tested by pressurisation, evacuation or sampling.
The seal may be constructed from a resilient deformable material such as an elastomer which is compressed by coplanar mating surfaces to provide a hermetic seal. To increase the compressibility and flexibility of the seal without undue increase in clamping force, the sealing rings may be hollow, vented and have a cross-sectional dimension perpendicular to the plane of the ring which is greater than the cross-sectional dimension in the plane of the ring.